It's stopped working a couple of times (unplugging, plugging in fixes it) under heavy load, but nothing like what it was before (which was unusable). However the speed is no better at 1000bt than it is at 100bt, so YMMV - that could also be down to my NAS appliance.

Apologies if this or something like it has already been mentioned — it's a long thread!

I have a brand-new Cisco gigabit managed switch, iMacs and MacBooks connecting to it fine at gigabit speeds. Two brand-new 2011 Mac Minis refused to

From hints here and elsewhere about IEEE 802.3, I eventually found that the Cisco's ports defaulted to having "flow control" turned off. It turned it on and the Mac Mini I was testing with immediately connected at 1000BaseT - problem solved! (Hopefully it sticks.)

I just spent my whole day rewiring my house with cat6, upgrading to 5th generation extreme base stations, replacing all switches with netgear gigabit switches and replacing all patch cables to cat6.

1 Signle stupid mac mini refuses to connect at 1000BaseT. When I connect the cable I can see it in the advanced hardware tab switching to 1000BaseT then diconnecing a few times. After 5 or so tries is settles and connects at 100BaseTX. I unglug cable from back of mac mini and plug it into macbook pro and boom instant 1000BaseT. What gives?? I have an older mac mini that works just fine. A new mac mini that works just fine. Tested all my laptops all connect no problem at 1000BaseT. Only this stupid 1.8 Core Duo mini running 10.5.8.

If I force it to 1000BaseT after connecting and disconnecting a while if finally connects but bandwith is about 0.

We also have a 2011 Mac Mini running Lion that refuses to connect at 1000BaseT. 10 foot Ethernet cable to the Airport Extreme in Bridge Mode, but all our other macs - imac and macbook pro - when using the SAME cable, connect with no problem at 1000BaseT. Any suggestions??? Help please!

Thanks for the tips Gerry, but it doesn't get me any further... When I go to manual and all the associated settings, it stops recognizing the cable. In automatic the speed goes automatically down to 100baseT. Since the same cable connected to the iMac and MacBook pro functions perfectly, I assume it's not the cable, but I did try switching it out, same sad results. Any other ideas would be most welcome!

It's a flow control collision between the Mac hardware/software & the switch. I solved it by upgrading to a better quality switch (see above). No amount of operating system tweaking or upgrades will solve it.

I have a new iMac and it has similar (though not as severe) upstream problems. I've got a new core switch coming that should solve that issue.

The real mystery is why this became a problem later rather than being a problem right at the begining. My guess is that Apple decided to change flow-control in a way that broke a lot of cheap switches...

I've upgraded operating systems twice - from Leopard to Snow Leopard to Lion and it's made zero difference. Neither has downgrading to a previous OS. Switching to better hardware, however, made a huge difference. 1000bt was stable. Basically, if your switch doesn't support 802.1x flow control (and most under about $150 don't), then you should look at that first.

But, hey, go ahead. If it fixes your problem, great, but you would be the exception rather than the norm...

If by saying that I'm connecting back 2 back two Macbooks you can see any switch present in the setup, then the beer is on me ! (with two other Macbooks here at work that functions without any problem in the same setup).

The flow control thing I already tried with one of those "cheap Cisco switches"

Will let you know how my quest goes and maybe I have more luck than the previous poster before me (Ladiv)

You're right, I didn't pickup on your linking them back to back. However, just because you hook up to machines back to back doesn't mean the flow control issues go away, it may actually make them worse - read the link I sent.

If you are using a Cisco switch (and you've made sure it has 802.1x, not all of them do - the old low-end Linksys line doesn't, for example), then I'm going to guess your hardware is bad like a couple of other people upthread.

The real test would be to install another OS (Windows, Linux or BSD) and see if you still have issues. If not, it's def. the software and downgrading to a known working version is the most sensible approach.

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